Modification to Generic Configuration of RTO Corrugated Ceramic Heat Recovery Media

ABSTRACT

The invention is in the form of a regenerative thermal oxidizer (RTO) comprising a chamber having a first opening into the chamber, a second opening into the chamber, a source of heat within the chamber, and one or more heat recovery media positioned within the chamber, each heat recovery media comprising plates having a first surface and an opposite second surface, wherein at least one plate has one or more openings passing from the first surface to the second opposite surface. The arrangement of the plates provides channels formed between adjacent plates and a flow of gas through the chamber is parallel with the channels

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a utility application claiming priority to provisional application No. 62/183,234 filed on Jun. 23, 2015, the contents of which are incorporated herein in their entirety by reference.

TECHNICAL FIELD OF THE INVENTION

The technical field of the invention relates to modifications to corrugated ceramic heat recovery media used in regenerative thermal oxidizers devices.

BACKGROUND OF THE INVENTION

Regenerative thermal oxidizers (RTO) use a ceramic heat sink heat recovery media to reduce the amount of fuel needed to elevate pollutants to their oxidation temperature of greater than 1400° F.

Process pollutants in the form of process off-gases are pushed or pulled into a heat recovery section of a RTO, which contains some configuration of a porous ceramic heat sink material, on their way to the combustion chamber where, with the firing of a burner, its temperature is elevated to greater than 1400° F., converting the pollutants to H₂O and CO₂. The hot products of combustion then pass through a second heat recovery chamber, again containing a porous ceramic heat exchange media, and exit the unit. In the second heat recovery chamber, approximately 95% of the heat contained in the products of combustion is absorbed by the media.

Next, through a series of switching valves, the flow direction through the RTO may be reversed such that the contaminated process gases pass through the second heat recovery chamber containing the stored heat on its way to the combustion chamber. Here the process gasses absorb the heat from the media, raising its temperature to within 5% of that needed in the combustion chamber for oxidation to occur.

The chamber flow reversal process is ongoing on a preprogrammed interval. By this means, there is a 95% reduction in the amount of burner fuel necessary to elevate the process gases to oxidation temperature. As should be understood, this use of a heat recovery media generates a significant cost savings advantage compared to other thermal oxidizers.

For instance, if the process temperature entering the RTO is 100° F., the heat absorption prior to entering the 100° F. combustion chamber will be approximately 1335° F., so in actuality it picked up 1235° F. degrees of stored heat. As a result of picking up this extent of stored heart from the media, only 65° F. degrees of burner heat must be added to bring the pollutants to the desired oxidation temperature of 1400° F.

Corrugated structured media is sold for use in RTO systems as a heat recovery heat sink. Sometimes it is used alone and sometimes it is added to random packed ceramic heat recovery media to increase the thermal efficiency and lower the unit's overall pressure drop.

One manufacturer markets the product under the trade name Flexeramic™, while another manufacturer markets a monolith media product under the trade name NK and/or with the number of cells per inch. Lantec Products markets a line of multi-layered media as MLM®, such as MLM-125, MLM-125-I, MLM-160, MLM-180, MLM-200 and MLM-S, that are described as being patented according to U.S. Pat. No. 6,071,593. FIG. 1 is taken from the '592 Patent and illustrates a stack of ceramic plates 10 having parallel upper ribs 14 and lower ribs 18 that extend from a wall surface 16 to form adjacent parallel groves 21 and 23, respectively. The grooves 21, 23 are formed into channels by being contacted with the surface of an opposing plate 10. Of relevance to the instant application, the plates do not contain holes through the walls 16 of the plate to provide openings between adjacent grooves or channels.

Corrugated structured media is typically a generic product manufactured in different block sizes, cell wall thickness, spacing, chemical composition and opposing plate inclinations, little or nothing has been done to resist particulate plugging in the generic configuration which can occur when contaminated process gases containing silica and other particulate pass through the media on the way to the combustion chamber and through the RTO. The only remedy, until now, is to make the wall spacing between larger, hopefully allowing more particulate storage space, and thus more time before particulate clogging stops the process flow through the RTO.

While structured, monolith and multi-layered products are sometimes touted as “clog” resistant, the reality is, when it comes to silica particulate plugging, it fairs equal to, or perhaps only marginally better, than some random packed products used for the same purpose in a RTO.

When three types of media plug, or any media for that manner, flow through the RTO ceases. When this occurs, some means must be used to unplug it, either by washing the product in place, hopefully washing the particulate out of the RTO, with marginal success, or removing the product, washing it and then replacing it, or the removal and replacement of the product entirely, which is usually the case.

To replace these products is a very costly endeavor, as not only is the RTO out of service until the media is remediated, but typically, depending on local pollution control jurisdiction, the process using the media must be halted. In such a circumstance, plant production must therefore stop. Replacement of ceramic media is expensive, costing in some cases hundreds of thousands of dollars. As such, anything that can be done to extend the longevity of the media is a significantly cost benefit.

Replacement interval of this media or any other type of heat recovery media, due to plugging, depends on the quantity of particulate in the process air stream. Typically media lasts between 1 and 3 years in a particulate laden environment, depending on the particulate concentration.

The modification to the generic structured, monolithic and multi-layered media described herein is believed to provide an improved life expectancy before plugging as compared to the known media, e.g., conventional structured, monolithic and multi-layered media.

SUMMARY OF THE INVENTION

In one general aspect the invention is in the form of a regenerative thermal oxidizer (RTO) comprising a chamber having a first opening into the chamber, a second opening into the chamber, a source of heat within the chamber, and one or more heat recovery media positioned within the chamber, each heat recovery media comprising plates having a first surface and an opposite second surface, wherein at least one plate has one or more openings passing from the first surface to the second opposite surface.

Embodiments of the regenerative thermal oxidizer may include one or more of the following features. For example, the configuration of the plates provides channels formed between adjacent plates and a flow of gas through the chamber is parallel with the channels.

The one or more openings in the plate may be perpendicular to the air flow through the one or more channels formed between adjacent plates. The one or more openings interconnect the one or more channels formed between adjacent plates.

The heat recovery media may be in the form of an extruded ceramic monolith heat recovery media. The heat recovery media may be in the form of a ceramic corrugated structured heat recovery media. The heat recovery media may be in the form of a ceramic multi-layered heat recovery media.

Each plate may include one or more openings. Alternatively, less than all of the plates present in each heat recovery media may include one or more openings.

In one embodiment, the heat recovery media may be in the form of an extruded ceramic monolith heat recovery media that contains numerous openings passing through the block and oriented to be in the opposite direction of gas flow, thereby interconnecting individual flow cells formed within the heat recovery media. In another embodiment, the heat recovery media may be in the form of ceramic corrugated structured heat recovery media containing numerous opening passing through the block and oriented to be in the opposite direction of gas flow, thereby interconnecting individual flow cells formed within the heat recovery media. In yet another embodiment, the heat recovery media may be in the form of a ceramic multi-layered heat recovery media containing numerous openings passing through the block and oriented to be in the opposite direction of gas flow, thereby interconnecting individual flow cells formed within the heat recovery media.

The openings may make up between about 10% to about 50% of the surface of the plate, between about 20% to about 40% of the surface of the plate, or between about 20% to about 30% of the surface of the plate.

The one or more openings in one plate may be aligned with the one or more openings in an adjacent plate. In another embodiment, the one or more openings in one plate are not aligned with the one or more openings in an adjacent plate.

The one or more openings in one plate may be of a different size than the one or more openings in an adjacent plate. A first percentage of opening provided by the one or more openings in one plate may be different from a second percent of opening provided by the one or more openings in an adjacent plate.

In another embodiment, the invention is directed to a method of treating a gas, the method comprising providing a regenerative thermal oxidizer (RTO) comprising a chamber having a first opening into the chamber, a second opening into the chamber, a source of heat within the chamber, and one or more heat recovery media positioned within the chamber, each heat recovery media comprising plates having a first surface and an opposite second surface, wherein at least one plate has one or more openings passing from the first surface to the second opposite surface. The method comprises:

passing the gas through the first opening into the chamber;

passing the gas through the first heat recovery media positioned within the chamber, whereby passing the gas through the first heat recovery media causes the gas to absorb heat from the first recovery media;

passing the gas past a burner to supply heat to the gas to cause an oxidation of the gas; and

passing the gas through the second heat recovery media positioned within the chamber, whereby passing the gas through the second heat recovery media causes the gas to transfer heat from the gas to the second recovery media.

The configuration of the plates provides channels formed between adjacent plates and the flow of gas through the chamber is parallel with the channels and perpendicular to the openings such that the gas passes through the channels and the openings in the first heat recovery media and the second heat recovery media.

The ceramic plates having holes or openings formed therein may provide numerous advantages, such as:

1. The holes may generate an alternate flow passage around a clogged media passage for the process gases to flow, as all the channels in the block will be interconnected by way of the holes.

2. The holes may generate flow turbulence that helps scour any lightly held dry particulate, such as silica dust, off the plate walls. This scouring effect loosens the particulate, re-entraining it back into the airstream, moving it through the RTO without clogging the media, thereby extending the service life of the media.

3. Since almost 99% of the pollutants in a RTO are destroyed within the recovery chamber where heat is stored, it is an advantage to generate the 3-Ts necessary for complete oxidation of pollutants: time, temperature and turbulence. Therefore a third benefit of the holes may be to create flow turbulence by removing the laminar flow created by the straight corrugated channel passages, thus giving the polluted gases random paths through heat recovery media.

4. The holes may slow down the velocity of the polluted gases by generating a longer flow path, thus generating additional time at the oxidation temperature for providing more complete destruction of pollutants to take place.

5. The holes may generate greater free flow area which allows the ceramic corrugated plates to be spaced close together without a higher pressure drop, thus generating a higher surface area from which the heat can be absorbed. This not only adds to the thermal efficiency by way of heat storage, but allows the transfer of recovery chambers fess frequently, improving overall destruction efficiency of the pollutants.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an image of prior art ceramic plates arranged in a block configuration.

FIG. 2 is an image of a prior art corrugated, ceramic plate arranged in a block configuration.

FIG. 3 is a drawing of a single corrugated ceramic plate.

FIG. 4 is a drawing of the single corrugated ceramic plate of FIG. 3 having holes or openings made in the plate to provide 20% of the surface consisting of an opening.

FIG. 5 is a drawing of the single corrugated ceramic plate of FIG. 3 having holes or openings made in the plate to provide 30% of the surface consisting of an opening.

FIG. 6 is an image of the corrugated ceramic plates having openings and arranged in a block configuration.

FIG. 7 illustrates a chamber in a regenerative thermal oxidizer having a pair of heat recovery media according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 2, in a generic corrugated product, a number of thin adjacent ceramic plates, typically greater than ten, are aligned at opposing angles to form a block configuration and then glued together using a ceramic adhesive. The end product for ease of handling is approximately 12″ cu., although they can be manufactured in other dimensions. Typically the opposing plate angle is 90, 45 or 30 degrees. The mating of the plates forms individual channels for air to flow through. The blocks are laid vertically and horizontally with the air passage channels parallel to flow. Blocks are laid adjacent to each other so that horizontal layers are formed in a RTO heat recovery chamber, so that the flow channel(s) from one block approximately aligns itself with the vertically aligned adjacent block on top or beneath.

Referring to FIGS. 3-5, according to one aspect of the invention, the manufacture of the structured, monolith or multi-layered ceramic RTO heat recover media includes an additional step of punching, drilling or otherwise forming multiple holes in the flat soft ceramic plates before they are corrugated, glued together and kiln fired. FIG. 3 illustrates a corrugated ceramic plate 100 that is made up of multiple pairs of parallel edges 105 that are connected by a wall portion 110 of solid ceramic material. FIG. 4 illustrates the corrugated ceramic plate 100 after openings or holes 115 are drilled, punched or otherwise formed through the wall portions 110. The openings 115 may be through the wall portion 110 only or through the adjacent wall portions and the edge 105 separating the wall portions 110. FIGS. 4 and 5 illustrate corrugated plate 100 having holes 115 formed through the plates. The plates of FIGS. 4 and 5 differ in the amount of open area through the plates with FIG. 4 showing approximately 20% open area and FIG. 5 showing approximately 30% open area. The amount of open area can be controlled by varying the size of the openings and/or the number of openings. FIG. 6 illustrates the plates 100 with numerous holes punched, drilled or otherwise formed through the wall of each plate and the plates being mounted together to form a block of corrugated plates.

It should be understood that the openings can also be formed in plates having the configuration illustrated in FIG. 1. Using the plates of FIG. 1 to illustrate this embodiment of the invention, the openings are formed in the wall surface 16 and extend between grooves 21 and 23. While the openings may be formed entirely in the wall surface 16, the openings may also be formed in part through the ribs 14, 18.

The multiple “through-the-block holes” are formed in a horizontal direction to air flow. While the holes may be formed before being kiln fired, the holes in the flat ceramic sidewalls also may be made after they are kiln fired. This step of punching holes is believed to be well within the ability of one of skill in the art and is not a difficult task. Following forming of the holes or openings, the plates are combined to form a block. The block contains flow cells or channels through the block through which gases can flow when the block is incorporated within a regenerative thermal oxidizer.

One or more block comprising the plates will be placed within a chamber of a regenerative thermal oxidizer. The arrangement of the ceramic plates is such that the layers, channels or flow cells formed by the plates are collinear with the gas flow of the regenerative thermal oxidizer while the openings in the surfaces of the plates are perpendicular or opposite to the direction of the air flow through the regenerative thermal oxidizer.

FIG. 7 illustrates a diagrammatic illustration of a regenerative thermal oxidizer 200 having a first opening 205 into a chamber 210 and a second opening 215 into the chamber. The chamber 210 includes a first heat recovery media 220, a second heat recovery media 225 and a burner 230. The heat recovery media 220, 225 are blocks formed from plates having one or more openings through the plate surfaces, e.g., from a first surface of the plate to a second opposite surface of the plate. In operation, the gas enters the chamber 210 through opening 205, as indicated by the solid directional arrows, passes through the first heat recovery media 220 and is heated by the chamber burner 230. The heated gas then passes through the second heat recovery media 225 and out of the chamber through opening 215. While passing through the second heat recovery media 225, heat in the gas is transferred to the heat recovery media 225.

As explained above, the flow of the gas periodically will be reversed, as indicated by the dashed arrows, such that opening 215 functions as an inlet for gas and opening 205 functions as an outlet. In this manner the gas will enter the chamber 210 through the opening 215, be heated by recovering heat from the media 225 and then receive additional heat by the chamber burner 230. The gas then will pass through the heat recovery media 220 and out the opening 205. As the gas passes through the heat recovery media 220, heat will be transferred from the gas to the media.

The arrangement of the ceramic plates is such that the openings formed through the plates are collinear with the gas flow while the surfaces of the plates are perpendicular to the air flow.

Holes will be large enough and spaced so that they overlap the channels. The alignment of plates may result in the holes or openings being aligned or offset. The block with plates may be arranged such that some plates have openings and other plates are free of openings. Further, plates may have a different number of openings, sizes of openings, or percentage of the surface being open in comparison to other plates within the block. Holes can either be of a slot, round, square or almost about any configuration that will suit the application. The invention is not limited by size, shape or spacing of the holes, nor is it bound by the block shape as it can have shapes other than a square block. The holes or openings may make up from 5-90%, from 10-80%, from 20-70%, from 30-60%, from 40-50% of the surface of the plates. The holes or openings may make up about 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or more of the surface of each plate, or individual values between the named values.

While several particular forms of the invention have been illustrated and described, it will be apparent that various modifications and combinations of the invention detailed in the text and drawings can be made without departing from the spirit and scope of the invention. Similarly, references to methods of construction, specific dimensions, shapes, utilities or applications are also not intended to be limiting in any manner and other materials and dimensions could be substituted and remain within the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims. 

What is claimed is:
 1. A regenerative thermal oxidizer (RTO) comprising a chamber having a first opening into the chamber, a second opening into the chamber, a source of heat within the chamber, and one or more heat recovery media positioned within the chamber, each heat recovery media comprising plates having a first surface and an opposite second surface, wherein at least one plate has one or more openings passing from the first surface to the second opposite surface.
 2. The regenerative thermal oxidizer of claim 1, wherein the configuration of the plates provides channels formed between adjacent plates and a flow of gas through the chamber is parallel with the channels.
 3. The regenerative thermal oxidizer of claim 2, wherein the one or more openings in the plate are perpendicular to the air flow through one or more channels formed between adjacent plates.
 4. The regenerative thermal oxidizer of claim 3, wherein the one or more openings interconnect the one or more channels formed between adjacent plates.
 5. The regenerative thermal oxidizer of claim 1, wherein the heat recovery media comprises an extruded ceramic monolith heat recovery media.
 6. The regenerative thermal oxidizer of claim 1, wherein the heat recovery media comprises ceramic corrugated structured heat recovery media.
 7. The regenerative thermal oxidizer of claim 1, wherein the heat recovery media comprises ceramic multi-layered heat recovery media.
 8. The regenerative thermal oxidizer of claim 1, wherein each plate comprises one or more openings.
 9. The regenerative thermal oxidizer of claim 1, wherein less than all of the plates present in each heat recovery media comprise one or more openings.
 10. The regenerative thermal oxidizer of claim 1, wherein the heat recovery media comprises extruded ceramic monolith heat recovery media containing numerous openings passing through the block and oriented to be in the opposite direction of gas flow, thereby interconnecting individual flow cells formed within the heat recovery media.
 11. The regenerative thermal oxidizer of claim 1, wherein the heat recovery media comprises ceramic corrugated structured heat recovery media containing numerous opening passing through the block and oriented to be in the opposite direction of gas flow, thereby interconnecting individual flow cells formed within the heat recovery media.
 12. The regenerative thermal oxidizer of claim 1, wherein the heat recovery media comprises ceramic multi-layered heat recovery media containing numerous openings passing through the block and oriented to be in the opposite direction of gas flow, thereby interconnecting individual flow cells formed within the heat recovery media.
 13. The regenerative thermal oxidizer of claim 1, wherein the openings comprise between about 10% to about 50% of the surface of the plate.
 14. The regenerative thermal oxidizer of claim 1, wherein the openings comprise between about 20% to about 40% of the surface of the plate.
 15. The regenerative thermal oxidizer of claim 1, wherein the openings comprise between about 20% to about 30% of the surface of the plate.
 16. The regenerative thermal oxidizer of claim 2, wherein the one or more openings in one plate are aligned with the one or more openings in an adjacent plate.
 17. The regenerative thermal oxidizer of claim 2, wherein the one or more openings in one plate are not aligned with the one or more openings in an adjacent plate.
 18. The regenerative thermal oxidizer of claim 2, wherein the one or more openings in one plate are of a different size than the one or more openings in an adjacent plate.
 19. The regenerative thermal oxidizer of claim 2, wherein a first percentage of opening provided by the one or more openings in one plate is different from a second percent of opening provided by the one or more openings in an adjacent plate.
 20. A method of treating a gas, the method comprising providing a regenerative thermal oxidizer (RTO) comprising a chamber having a first opening into the chamber, a second opening into the chamber, a source of heat within the chamber, and one or more heat recovery media positioned within the chamber, each heat recovery media comprising plates having a first surface and an opposite second surface, wherein at least one plate has one or more openings passing from the first surface to the second opposite surface, the method comprising: passing the gas through the first opening into the chamber; passing the gas through the first heat recovery media positioned within the chamber, whereby passing the gas through the first heat recovery media causes the gas to absorb heat from the first recovery media; passing the gas past a burner to supply heat to the gas to cause an oxidation of the gas; and passing the gas through the second heat recovery media positioned within the chamber, whereby passing the gas through the second heat recovery media causes the gas to transfer heat from the gas to the second recovery media, wherein the configuration of the plates provides channels formed between adjacent plates and the flow of gas through the chamber is parallel with the channels and perpendicular to the openings such that the gas passes through the channels and the openings in the first heat recovery media and the second heat recovery media. 